package com.lagou.sqlSession;

import com.lagou.pojo.Configuration;
import com.lagou.pojo.MappedStatement;
import org.apache.commons.lang3.StringUtils;

import java.lang.reflect.*;
import java.util.List;

public class DefaultSqlSession implements SqlSession {

    private final Configuration configuration;

    public DefaultSqlSession(Configuration configuration) {
        this.configuration = configuration;
    }

    @Override
    public <E> List<E> selectList(String statementId, Object... params) throws Exception {
        //将要去完成对simpleExecutor里的query方法的调用
        SimpleExecutor simpleExecutor = new SimpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
        List<Object> list = simpleExecutor.query(configuration, mappedStatement, params);
        return (List<E>) list;
    }

    @Override
    public <T> T selectOne(String statementId, Object... params) throws Exception {
        List<Object> objects = selectList(statementId, params);
        if (objects.size() == 1) {
            return (T) objects.get(0);
        } else {
            throw new RuntimeException("查询结果为空或者返回结果过多");
        }


    }

    @Override
    public <T> T getMapper(Class<?> mapperClass) {
        // 使用JDK动态代理来为Dao接口生成代理对象，并返回

        Object proxyInstance = Proxy.newProxyInstance(DefaultSqlSession.class.getClassLoader(), new Class[]{mapperClass}, new InvocationHandler() {
            @Override
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                // 底层都还是去执行JDBC代码 //根据不同情况，来调用selctList或者selectOne
                // 准备参数 1：statmentid :sql语句的唯一标识：namespace.id= 接口全限定名.方法名
                // 方法名：findAll
                String methodName = method.getName();
                String className = method.getDeclaringClass().getName();
                String statementId = className + "." + methodName;
                // 准备参数2：params:args
                // 获取被调用方法的返回值类型
                MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
                if (StringUtils.equals(mappedStatement.getSqlType(), "select")) {
                    Type genericReturnType = method.getGenericReturnType();
                    // 判断是否进行了 泛型类型参数化
                    if (genericReturnType instanceof ParameterizedType) {
                        return selectList(statementId, args);
                    }
                    return selectOne(statementId, args);
                } else if (StringUtils.equals(mappedStatement.getSqlType(), "insert")) {
                    return insertUser(statementId, args);
                } else if (StringUtils.equals(mappedStatement.getSqlType(), "update")) {
                    return updateUser(statementId, args);
                } else if (StringUtils.equals(mappedStatement.getSqlType(), "delete")) {
                    return deleteUser(statementId, args);
                }
                return null;
            }
        });
        return (T) proxyInstance;
    }

    private Object insertUser(String statementId, Object... args) throws Exception {
        SimpleExecutor simpleExecutor = new SimpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
        return simpleExecutor.insert(configuration, mappedStatement, args);
    }

    private Integer updateUser(String statementId, Object... args) throws Exception {
        SimpleExecutor simpleExecutor = new SimpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
        return simpleExecutor.update(configuration, mappedStatement, args);
    }

    private Integer deleteUser(String statementId, Object... args) throws Exception {
        SimpleExecutor simpleExecutor = new SimpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
        return simpleExecutor.delete(configuration, mappedStatement, args);
    }


}
